Lubricant compositions containing dialkyl diselenides



Patented Oct. 31, 1950 UNITED, STATES, PAT NT OFFICE LUBRICANTCOMPOSITIONS CONTAINING DIALKYL DISELENIDES George H. Denison, Jr.,Oakland, and Paul C. Condit, Berkeley, Calii'., assignors to CaliforniaResearch Corporation, San Francisco, Calif., a

corporation of Delaware No Drawing. Application June 4, 1945,

Serial No. 597,594

' small amount of an oxidation inhibitor. Thus, it is now a commonpractice to add to an oxldizable organic substance a small amount, 0.1%or less to 1% or more, by weight, of a sulfur compound such as dicetylsulfide, or a phenolic compound such as 2,6-ditertiary butyl p-cresol,or a nitrogen compound such as a-naphthylamine. These and otherstabilizers or oxidation inhibitors are added to mineral lubricatingoils, fatty oils, rubber, etc. 4

It is desirable that the stabilizer or inhibitor be easily andeconomically prepared in commercial quantities from readily availablematerials; that it be soluble in the material to which it is added; thatit be stable and non-corrosive; that it be potent in its stabilizing andinhibiting action; and that it have a long life as a stabilizer orinhibitor.

It is an object of the present invention to stabilize oxidizable organicsubstances.

It is a particular objectof the invention to stabilize hydrocarbonlubricating oils against oxidation.

It is a further object of the invention to provide a class ofstabilizers or oxidation inhibitors which are easily and economicallyprepared from readily available materials.

It is a still further object of the invention to provide a class ofstabilizers or oxidation inhibitors which are soluble in viscoushydrocarbon oils and other organic substances of similar solventproperties.

It-is a still further object of the invention to provide a class ofstabilizers or oxidation inhibitors which are stable and non-corrosive.

It is a still further object the invention to 5 Claims. (Cl. 252-45)provide a class of stabilizers or oxidation inhibitors which are potentin their stabilizing and inhibiting action,-

It is a still iurther object of the invention to provide a class ofstabilizers or oxidation inhibitors which have a long life in theirintended use as stabilizers or inhibitors.

It is a still further object of the invention to provide a class ofstabilizers or oxidation inhibitors which combine several desirableproperties v such as ease of preparation, oil-solubility, stability andnon-corrosiveness, potency and long life.

It has been discovered that the aliphatic diselenides, compounds of theformula wherein the carbon atoms shown are aliphatic carbon atoms, arepotent stabilizers or oxidation inhibitors for oxidizable organicsubstances.

Some of the aliphatic diselenides herein disclosed are old per se whileothers are new. They are all easily prepared from readily availablematerials, the principal cost factor being the cost of selenium. All ornearly all of the most easily available, unsubstituted aliphaticdiselenides (those in which the aliphatic groups are purely hydrocarbon)are readily soluble in hydrocarbon lubricating oils and other organicsubstances having similar solvent properties. They are relatively stableand non-corrosive. They are very potent oxidation inhibitors and have anunusually strong stabilizing effect on mineral lubricating oils and thelike. In this respect, it is believed that the aliphatic diselenides areno more potent on an equivalent selenium basis than the aliphaticmonoselenides (seleno ethers -R.-S e-R) which are disclosed and claimedin our copending application, Serial No. 476,760, but

since the diselenides contain much more selenium n; thehigher molecularweight compounds, al-

most twice as much selenium) than the analogous monoselenides, theyoiler the advantage that much more selenium can be incorporated in anoil or other oxidizable substance, per weight of added seleniun-iccompound, than can be incorporated when adding the same weight oi.monoselenide.

I Among the presently available methods of preparing the diselenides,which, as stated, are an important factor in the commercial utility ofan oxidation inhibitor, are the following:

(1) By condensing sodium diselenide (or potassium diselenide) with analiphatic halide. The reaction is as follows:

This method is illustrated by the preparation of dioctadecyl diselenidedescribed below in Example 2.

(2) By oxidation of a seleno mercaptan:

This method may be carried out by contacting the seleno mercaptan withair or oxygen. The structure of the product is believed to be as shown,but we do not know definitely whether the diselenides oi the inventionhave the Se-Se or the II Se group or are mixtures of both types ofcompound. (3) An alkali metal seleno cyanate (e. g., NaSeCN) isconverted to an aliphatic seleno cyanate, which can be converted to adiselenide by treating with caustic alkali in aqueousalcohol. Thereactions involved are R- Cl +NaSeCN- RSeCN+NaCl This reaction isillustrated by the preparation of dilauryl diselenide described inExample 1 below. The advantages of this method are twofold: First, it isnot necessary to prepare sodium diselenide, which, by, previously knownmethods, is troublesome to prepare and involves the use of metallicsodium. Second, the final reaction products are the desired diselenideand cyanogen gas, the latter being easily removed without leaving animpurity.

(4) By heating an aliphatic monoselenide with an equivalent weight ofselenium:

In the above equations, R represents an aliphatic radical (includingaryl substituted aliphatic radicals such as the benzyl radical) and thetwo Rs in a given compound may be the same or difl'erent radicals.

The diselenides of the invention have this further advantage: As noted,they contain more selenium per given weight of compound than themonoselenides. On the other hand, they are more stable than triandhigher polyselenides (RSea-R, Mei-R, etc); these latter split oil freeselenium readily, or behave like free selenium, cause the free seleniumdiscolors the substance stabilized or metal surfaces contacted by thestabilized material. Thus, the diselenides, although less stable thanthe monoselenides, are sufficiently stable for many purposes andrepresent in certain cases an optimum balance between maximum stability(exhibited by the monoselenides) and maximum selenium content (exhibitedby the triand higher polyselenides).

Also, the aliphatic diselenides are more advantageous than the aromaticor even the mixed aromatic-aliphatic diselenides, for they are moreeasily prepared and are more potent oxidation inhibitors.

Examples of suitable aliphatic diselenides are dipropyl, di-n-butyl,di-isobutyl, di-n-amyl, di- 7 which is in many cases undesirablebeiso-amyl, dihexyl, diheptyl, dioctyl, didecyl, dilauryl, dicetyl,dibenzyl, di-cetylbenzyl and dicyclohexyl diselenides; mixed diselenidessuch as methyl propyl, cetyl ethyl and butyl benzyl diselenides;mixtures of diselenides such as produced when a halogenated mixture ofhydrocarbons such as chlorinated naphtha, chlorinated kerosene orchlorinated paraflin wax is used as the reactant RC1 in methods (1) and(3) above; and aliphatic diselenides having non-hydrocarbon substituentson the hydrocarbon radicals, such as chlorine, bromine, hydroxyl andamino.

The preferred diselenides are those containing not less than 8 nor morethan 30 carbon atoms in each hydrocarbon (or substituted hydrocarbon)radical. Thus, these compounds are oilsoluble and are not appreciablyvolatile at temperatures of about 300 F. Also, they are easily preparedfrom readily available, non-volatile liquid or solid materials.

The diselenides may be used in amounts as low as 0.01% or less or ashigh as 5% or more, but preferably they are used in amounts of 0.1 to2%, percentages being by weight based on finished composition.Concentrates or stock solutions containing 50% or more of diselenidedispersed in an organic liquid (e. g., mineral lubricating oil) may beprepared for later blending with the substance to be stabilized toproduce a finished product.

Illustrative of organic substances to which the diselenides may be addedas stabilizers are petroleum products such as gasoline, kerosene,lubricating oils and mineral oil-soap greases; fats, fatty oils, rubber,aldehydes, ethers, terpenes, mercaptans, phenols and synthetic plasticor resinous materials such as urea-formaldehyde. polyvinyl andphenol-formaldehyde resins. These and other organic materials undergooxidation and deterioration (e. g., discoloration, sludge formation,thickening, etc.) under conditions ranging from mere exposure to air atnormal atmospheric temperatures to intimate admixture with air or otheroxidizing-gases at temperatures F. The inherent stability of the organicmaterial toward oxidation will, of course, vary with the material. Theselenium compounds of the invention will stabilize such materials undermild to extreme conditions of oxidation.

The following specific examples will serve to illustrate the practiceand advantages of the invention.

Example 1.-Dilauryl diselenide was prepared as follows: 10 grams oflauryl seleno cyanate (C12Hz5SeCn) were dissolved in 25 cc. of alcoholand the solution was cooled to 32 F. Two cc. of 50% aqueous NaOH werediluted with 10 cc. of alcohol and similarly cooled. On mixing the twosolutions a clear solution resulted which, however, began to deposit asolid in about 10 seconds and the solution then set to a solid. Anadditional 25 cc. of alcohol were stirred in and the mixture was allowedto stand at 40 F. for 2 hours. It was then poured into water and the oilthat separated was extracted with ethyl ether. The ethyl ether extractwas washed with water and dried over sodium sulfate and the etherremoved by evaporation. The residue was crystallized from a mixture ofether and alcohol. The resulting product consisted of fine, pale yellowplates melting at about 21 C.

5 Example 2.Dioctadecyl diselenide was prepared as follows: A mixture of2 gram moles of sodium diselenide, 2 gram moles of octadecyl chlorideand one liter of 95% ethyl alcohol were refluxed and stirred for ninehours. The reaction mixture was diluted with one liter of water andextracted with petroleum ether. The petroleum ether extract was driedover anhydrous sodium sulfate, filtered and concentrated on a steambath. Two volumes of a 50% mixture of petroleum ether and acetone wereadded and the solution was cooled to promote crystallization of thedioctadecyl diselenide. A yield of 602 grams of dioctadecyl diselenidewas obtained in the form of lemon yellow crystals melting at 52 C. to 55C. Analysis. Found; Se=22.3. Theoretical; Se=23.8.

Example 3.A highly refined SAE 30 Western oil and the same 011containing dissolved therein 0.1% by weight of dilauryl diselenide weresubmitted to an oxidation test in apparatus of the type described byDornte in Industrial and Engineering Chemistry, vol. 28, page 26 (1936),oxygen being absorbed by the oil under test at 340 F'. Results are setforth in Table I below, the figures in the second and third columnsdenoting cc. of oxygen absorbed by 100 cc. of oil. For comparison, dataon dicetyl sulfide and diphenyl selenide at concentrations of 0.1% byweight are also set forth in the table.

Table I Oxygen Absorbed by Base Oil Plus g Nil Dileuryl DiphenylDiselenide Selenide aersmr pppp pppp 5888888388l88528 Example4.Dioctadecyl diselenide was submitted to the same oxidation test, thediselenide being dissolved in the amount of 0.08% by weight in medicinalgrade white 011. The induction period (time for 100 grams of oil toabsorb 1200 cc. of oxygen) was found to be 2.5 hours. Under the sameconditions, dicetyl sulfide had an induction period of only 0.15 hourwhile dicetyl selenide had an induction period of 2.6 hours, both thesulfide and selenide being used in the amount of 0.1% by weight.

One or more diselenides of the invention may be used as the only addedmaterial present in an oxidizable organic substance or they may be usedin. conjunction with other additives. For example, the diselenides ofthe invention may be used advantageously in mineral lubricating oils inconjunction with metal salts of organic acids and/or metal salts oforgano-substituted inorganic acids. These salts are used to improvevarious properties of lubricating oils, such as detergency, stabilityagainst oxidation, film strength, etc. Examples of such metal salts arecalcium, barium, zinc and aluminum salts of cetylphenol; calcium,barium, zinc and aluminum salts of diamyl diphenol monosulfide; calcium,

asaaaae barium, zinc and aluminum salts of monoand dicetyl esters ofphosphoric acid; calcium, bar-- ium, zinc and aluminum salts of monoanddicetylphenyl esters of ditluophosphoric acids; calcium, barium, zincand aluminum salts of naphthenic acids; calcium, barium, zinc andaluminum salts of oil-soluble petroleum (mahogany) sulfonic acids;calcium, barium, zinc and aluminum salts of dibutyl dithiocarbamic acid;calcium, barium, zinc and aluminum salts of the reduced petroleumnitrogen base dithiocarbamates of Miller and Rutherford United StatesPatent No. 2,363,012. Other metals (e. g., sodium,

lithium, magnesium and cobalt) and other acid radicals (e. g., arylcarboxylic acid, fatty acid, aliphatic polycarboxylic and thiophenolradicals) may be used instead of the aforementioned calcium, barium,zinc and aluminum metals and the aforementioned phenate, phenatesulfide, phosphate, thiophosphate, naphthenate, sulfonate anddithiocarbamate radicals, respectively. Thus, from 0.1 to 2% ofdiselenide and from 0.1 to 2% of metal salt may be added to minerallubricating oil, orgreater amounts may be used to form a concentrate orstock solution. Flu'ther details concerning the conjoint use ofdiselenides and metal salts of organic and/or organo substitutedinorganic acids in oils of lubricating viscosity, such as particularcombinations of additives, results obtainable by such conjoint use,etc., may

be found in our aforesaid copending application Serial No. 486,306, andsuch details are mcorporated herein by reference.

The following example is illustrative of the beneficial effect of thediselenides 0f the invention in mineral lubricating oils in combinationwith metal salt additives.

Example 5.A Western SAE 60 aviation grade oil compounded with about 56%of a sulfurized calcium alkyl phenate (the calcium cetyl phenatesulfurreaction product of Etzler and Farrington United States Patent No.2,360,302) and about 0.12% of calcium cetyl phosphate was submitted tothe "Aluminum Dish Test. This test, which is very severe from thestandpoint of gum formation, was carried out as follows: A weighedsample of 011 (about 5 drops) was placed in an aluminum dish 2 inches indiameter which is flat on its lower face and slightly concave on itsupper face, the dish having been thoroughly cleaned and dried beforeputting in the oil. The dish was then placed on an electric hot plate,the surface temperature of which was adjusted to the desired value. Thedish was left on the hot plate for 20 minutes and was then removed andcooled to The dish and deposit were room temperature. then washed freeof oil with petroleum ether and the residual gum was determined. The gumis expressed as percentage by weight of the original oil. Other oilssubmitted to the same test were the same compounded oil containingcertain selenium compounds. Results are shown in Table II below.

The diselenides of the invention may also be used. advantageously inturbine lubricants and other industrial lubricants which are used tolubricate metal surfaces under conditions (such as intermixture of thelubricant with water) which promote rusting and corrosion of ferrousmetal surfaces. It is now the practice to add to such lubricants both acorrosion or rust inhibitor and an anti-oxidant. Examples of corrosionor rust inhibitors are lauryl acid maleate and the products ofcondensing high molecular weight olefins with maieic anhydride andhydrating the resulting condensation product. The said olefln-maleicanhydride condensation-hydration products are described in Moser, UnitedStates Patents Nos. 2,124,628 and 2,133,734. The diselenides of theinvention are especially advantageously used in turbine lubricants andothers of the class just described, in conjunction with rust orcorrosion inhibitors such as lauryl acid maleate or one of the aforesaidolefin-maleic anhydride condensation-hydration products. The diselenidescooperate with the rust or corrosion inhibitors to produce an oil whichis both stable and rust inhibitive. Amounts of diselenide ranging fromabout 0.1% or less to 2% or more and of rust or corrosion inhibitorsranging from 0.005% or less to 2% or more, preferably 0.05 to 0.5%, maybe used Moreover, the diselenides of the invention also function as filmstrengthening agents (E. P." agents) in lubricants.

We claim:

1. A lubricant comprising a major proportion of oil of lubricatingviscosity which is susceptible to deterioration when exposed to oxygenat ele- 3 vated temperatures and a small amount, suillcient to inhibitsuch deterioration, of a dialkyl diselenide selected from the groupconsisting of dilauryl diselenide. dicetyl diselenide and diparafllndiselenide.

2. A lubricant comprising a major proportion of an oil of lubricatingviscosity which is susceptible to deterioration when exposed to oxygenat elevated temperatures and a small amount. suificient to inhibit saiddeterioration, of dilauryl diselenide.

3. A lubricant comprising a major proportion of an oil of lubricatingviscosity which is susceptible to deterioration when exposed to oxygenat elevated temperatures and a small amount, sufflcient to inhibit saiddeterioration, of diparailin diselenide.

4. A lubricant comprising a major proportion of a mineral oil oflubricating viscosity and about 0.1 to 2% by weight based on finishedlubricant of dilauryl diselenide.

5. A lubricant comprising a major proportion of a mineral oil oflubricating viscosity and about 0.1 to 2% by weight based on finishedlubricant of dicetyl diselenide.

GEORGE H. DENISON, JR. PAUL C. CONDIT.

REFERENCES crran The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. A LUBRICANT COMPRISING A MAJOR PROPORTION OF OIL OF LUBRICATINGVISCOSITY WHICH IS SUSCEPTIBLE TO DETERIORATION WHEN EXPOSED TO OXYGENAT ELEVATED TEMPERATURES AND A SMALL AMOUNT, SUFFICIENT TO INHIBIT SUCHDETERIORATION, OF A DIALKYL DISELENIDE SELECTED FROM THE GROUPCONSISTING OF DILAURYL DISELENIDE, DICETYL DISELENIDE AND DIPARAFFINDISELENIDE.